Flowserve L75 Series Electric Actuator - Manual (Page 8)

L75 Series Electric Actuator — Modbus RTU FCD LMAIM7502-00 – 07/05

Configuration
The data link layer of communication conforms to the Modbus RTU specification. Slaves (actuators)
reply on the bus only in response to a valid command from the master control unit addressed to the
actuator. Each actuator has an address selected with switches on the actuator board. An actuator can
have any address from 1 to 247. (Modbus address 0 is reserved for broadcast messages). The address
is specified using two hexadecimal rotary switches. If an illegal address is set in the switches, the
actuator will not respond to any commands.
Modbus Address Selection
The Modbus address may be between 1 and 247 (decimal) or 01 and F7 hexadecimal. Address 0 is used
for broadcast messages only. Two on-board, rotary hexadecimal switches are used to set the address.
Remember the addresses on the switch must be specified in hexadecimal—not decimal. Be sure the
address is correctly set on the switches. If an invalid address is set, the SW3, SW4 and COMM LEDs
will blink simultaneously and the unit will not be operational.
Figure 2: Node Address
0 F
E
D
C
B
A
9 8 7
6
5
4
3
2
1 0 F
E
D
C
B
A
9 8 7
6
5
4
3
2
1
MSD LSD
Baud Rate Selection
Communication data rate is jumper-selectable as either 9600 bits per second or 19,200 bits per second.
Other communication parameters are fixed at no parity, 8 data bits, and 1 stop bit. Set the baud rate by
positioning the jumper as required for the appropriate transmission rate.
Two-Wire or Four-Wire Bus Selection
The RS-485 Modbus bus can be set to operate in either a two-wire or four-wire configuration. Set the
on-board jumpers as required for the desired configuration. Be sure that both jumpers are set for the
desired configuration. In either case, termination resistors are not required at segment ends.
Modbus Functions
The actuator supports the Modbus RTU protocol only. The actuator supports the following Modbus
functions:
Function Code Function Name Description
1 Read coil status State of motion control
2 Read input status State of limit switches
3 Read holding register State of actuator operation
5 Force single coil Starts/Stops actuator
6 Preset single register Starts/Stops actuator